Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$222.92	6.254%	$236.8614	$236.86	$236.85	$236.90
Purchase #2	$236.99	13.158%	$268.1731	$268.17	$268.15	$268.20
Purchase #3	$10.94	3.171%	$11.2869	$11.29	$11.30	$11.30
Purchase #4	$37.31	4.515%	$38.9945	$38.99	$39.00	$39.00
Purchase #5	$173.53	6.792%	$185.3162	$185.32	$185.30	$185.30
Purchase #6	$57.45	6.626%	$61.2566	$61.26	$61.25	$61.30
Purchase #7	$155.56	11.786%	$173.8943	$173.89	$173.90	$173.90
7 purchase totals =	$894.70		$975.7830	$975.78	$975.75	$975.90